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Considered one of the oldest cultivated plants, onions are thought to have originated in Central Asia. They have been cultivated for 5,000 years, but were likely consumed long before that because, like now, they were easy to grow in a wide variety of soil types, transportable, and a healthy food source.
Green onions, also known as salad onions, bunching onions, or scallions, are the young growth before the onion bulb forms. Popular raw, in salads, and in cooking for their mild flavor, they are also popular with home gardeners due to their ease in growing and economy of space. Shallow-rooted, they are equally easy to harvest.
Growing Green Onions at a Glance
Common Name: Green onions
Scientific Name: Allium fistulosum
Hardiness Zone: 3-9
Soil: pH 6.0-7.0; sandy, loamy, well-drained
Light: Full sun, 8 hours/day
Water: 1 inch per week
Food: Balanced, can amend with organic matter
Propagation: Division or seed
Safety: Toxic to cats and dogs; overconsumption can lead to gastrointestinal issues in humans
Green Onion Characteristics
Green onions (Allium fistulosum) are part of the onion family that includes onion, garlic, leeks, shallots, and chives. Green onions feature tubular (hollow) upright green leaves rising 1 to 2 feet from small white or light green bulbs (despite green onions being considered “bulbless”).
Green onions are now grown in about 170 countries. Ready to harvest in 60 to 95 days, they’re fast growers typically snipped or pulled long before they become a flowering green onion. Considered a “low-effort, high-reward crop,” they can grow just about anywhere.
Some consider any onion picked before they’re fully grown to be green onions. These young green onion sprouts are more tender and sweeter than the mature vegetable, making them popular for eating raw and for cooking.
Recommended Green Onion Varieties
Various types of green onions not only look different, but have unique flavors. Some of the most common kinds include:
- Welsh onions: With a flavor stronger than other green onions, this variety is chosen to add a zest to savory dishes.
- Chinese onions: Its thin green leaves and bulbs resemble scallions. The flowers of this mild-tasting onion are often used as a garnish.
- Red Beard: Easy to identify because of its red bulbs and long, slender leaves, this mild-tasting variety comes from China and Kazakhstan. It matures in a rapid 40 to 50 days.
- Japanese bunching onions: Featuring long white stems and deep green leaves, this variety offers mild to moderate pungency.
- Evergreen hardy white: This variety does well in colder weather and features a compact bulb and bright white stalks that have a pale green hue towards the top.
- Guardsman: A quick-growing variety ready to harvest in 60 days, it was produced from a cross between a bunching onion and a bulb onion, so it has the shape of a bunching onion with a strong root system and a larger top. It has the mildness of a bulb onion.
- Nabechan: This Japanese variety has a sweeter, more complex flavor. Its upright plants feature long, thick shanks that resist leaf-curl and bulbing in hot weather.
Planting Green Onions
Green onion cultivation is pretty straightforward. They can be direct-sown in the garden in the spring or started early inside to get a head start.
When is the best time to plant green onions?
Most gardeners plant green onions as early in the spring as soil conditions and temperatures allow, although some may start seeds indoors before it’s time to plant outside.
“In mild climates, plant them year-round. In colder zones, start seeds indoors 6 to 8 weeks before the last frost or direct-sow as soon as the soil is workable in spring,” advises Valeria Nyman, chief product officer at Taim.io, a platform that helps people grow their own food.
Where can green onions grow?
Nyman calls green onions “the street food of the garden world—resilient, adaptable, and happy just about anywhere.” Indeed, they can grow in garden beds, raised beds, or containers filled with neutral, well-draining soil that is kept moist. For succession harvesting, additional onions can be planted throughout the summer.
They prefer full sun, but can tolerate some shade, especially because they’re being harvested early.
How do you plant green onions?
To learn how to plant green onions, follow a few easy steps.
- Ensure the bed or container is weed-free before planting because weeds compete for water and nutrients. It’s difficult to pull large weeds without disturbing young plants.
- Plant green onion seeds about ¼ inch deep.
- Thin green onion seedlings to 2 inches apart.
- If transplanting seedlings, plant in the garden at the same depth at which they were growing in the container. This is done once seedlings are 3 to 5 inches tall.
- Space plants 2 to 3 inches apart in rows 1 to 2 feet apart.
Can you grow green onions in containers?
You can grow green onion from seeds in a container outside. Select a pot at least 12 inches deep with drainage holes. “The key is good drainage,” Nyman advises. “Green onions hate sitting in soggy soil.”
Fill the container with well-draining potting soil. Sow seeds ¼ inch deep and water to moisten the soil. Repotting isn’t necessary if the container is large enough and you harvest regularly so the green onions don’t get overgrown.
Watering Green Onions
Because green onions have shallow roots, regular watering is necessary when there’s insufficient rainfall. “Water deeply once or twice a week, depending on weather,” Nyman advises. “They like steady moisture but won’t tolerate drowning.”
Sitting in wet soil leads to rot and disease, but scallions are sensitive to drought. An average of 1 inch of water per week should keep the soil moist but not soggy. Soaker hoses or drip irrigation works well. Adding a layer of mulch can help reduce moisture evaporation.
Fertilizing Green Onions
Onions are known to be heavy feeders. Because scallions are leafy greens, they benefit from regular fertilization with a nitrogen-rich amendment. Nyman suggests a balanced organic feed (10-10-10) every few weeks to keep them “perky.” Other experts advise choosing fertilizer for green onions that is high in nitrogen (the “N” in N-P-K).
Liquid fertilizers distribute nutrients immediately, but slow-release granular fertilizers can reduce application frequency. Green onions also benefit from adding compost to the soil before they’re planted.
Pruning Green Onions
Pruning is typically only necessary on green onions to remove wilted or damaged leaves. It can also be done to prevent seed drop if they start to bolt. To direct the plant’s energy towards leaf development, trim the bud and stalk (called an onion scape) in the early stages of development. Leaf wilt is common during flowering, so unless you intend to gather seeds, it’s a good idea to trim off flower stalks.
Harvesting is the main form of “pruning” done to green onions.
Propagating Green Onions
There’s not a lot to know about how to propagate green onions because they handle the job on their own for the most part. Easily grown from seed, another way to propagate a scallion green onion is to plant them in late fall and overwinter them in the garden. By spring, you should see new growth.
You can even regrow green onions from the rooted green onion bulbs of store-bought green onion plants by placing them in moist soil either in the garden or indoors under a fluorescent light.
Safety Considerations
Even in small amounts, green onions are toxic to cats and dogs. The compound thiosulfate contained within the plant causes the breakdown of red blood cells, leading to anemia or a condition called hemolytic anemia, which can be life-threatening. Symptoms may not occur immediately, but there is a cumulative effect if onions of any kind are repeatedly given to them. It’s advisable to contact your veterinarian or a poison control hotline if you suspect they ingested green onions.
Although onions are a good source of nutrition for humans, overconsumption can cause gastrointestinal discomforts such as gas, bloating, fatigue, indigestion, and abdominal cramps.
Potential Pests and Diseases
Green onions are susceptible to a number of pests and diseases: cutworms, onion maggots, onion nematodes, slugs, thrips, aphids, allium leaf miner, mildew, leaf spots, downy mildew, rust, botrytis leaf blight, root rot, slugs, and snails. Nyman says thrips and onion maggots are the “main troublemakers.”
Preventive measures include crop rotation, drip irrigation to provide the proper amount of moisture without overwatering, removing weeds that harbor pests, and ensuring good air circulation around your plants by incorporating adequate spacing between plants, which also allows maximum sunshine.
Harvesting Green Onions
Green onions are wonderful companion plants to other garden vegetables because their odor wards off a number of pests, but the primary reason most people grow them is to eat them, so it’s important to know when and how to harvest these tasty greens.
When is the best time to harvest green onions?
Green onions are ready for harvest when they reach 6 to 8 inches tall and have a diameter similar in size to that of a pencil—roughly about ¼ to ¾ inch in diameter. This should occur in about 60 to 90 days after seeding, depending on the cultivar and the weather conditions.
If you are growing green onions as a perennial, it’s best not to harvest them in their first season in order to allow the plant to become established and produce a more bountiful crop the following season.
How do you harvest green onions?
Methods of harvesting depend on whether you’re collecting just some of the stems or taking the entire plant. For a cut-and-come-again approach, Nyman says, trim the tops, leaving the white base in the ground to regrow.
- Choose the largest stems; these mature stems are usually the outer ones.
- Using a clean pair of scissors or a sharp knife, gently cut about one-third of the green leaves close to the base without disturbing the white bulb or the roots.
How do you store green onions?
Green onions have a short shelf life of 7 to 10 days and are best used fresh. However, they can last a couple weeks in the refrigerator if wrapped in a damp paper towel that is placed inside a plastic bag kept in the crisper section.
For long-term storage, rinse and dry them before chopping. Then place them in freezer bags in an airtight container before putting them in the freezer. You can also dehydrate them and grind them into a powder.
